Major focus of previous research in the MACS has been the description of the rates of disease progression (from incubation period to trajectories of immunological markers) and the determination of factors associated with transmission and disease progression among those infected. The MACS has accumulated longitudinal data and a repository of samples over a span of ten years in a large number of participants. We have characterized subsets of individuals with patterns of immunologic markers that are indicative of immunity, for which the elucidation of correlates is of central importance. The Center for Analysis and Management of MACS Data (CAMACS) will continue to provide methodologic expertise in the design and analysis of MACS-wide studies, including the development of new procedures for the analysis of MACS data. Of particular importance for the extension of the cooperative agreement is the provision of statistical and epidemiological expertise in the design and analysis of HIV pathogenesis to compare subsets of the cohort with contrasting patterns of disease progression in individuals who are comparable with respect to known factors associated with disease progression (e.g., CD4 cell count). CAMACS will coordinate data acquisition, maintain and expand standardization procedures for transferring, editing, merging, storing and backing up the data. CAMACS will participate in study working groups and writing committees. CAMACS will revise the current public use data tape annually. Data will be organized in files readily usable by SAS and will reside in a SUN 69OMP networked with SUN SPARCstations. Software includes ORACLE, SAS, S and EGRET. Investigators have expertise in relevant areas of epidemiology/statistics for cohort studies of the nature of the MACS (e.g., longitudinal data: continuous and categorical; survival analysis: truncation, censoring, parametric and nonparametric methods). Epidemiologic expertise for properly nesting substudies within the cohort will be provided. The methodological expertise offered by CAMACS will contribute to the appropriate design of HIV pathogenesis studies and to the interpretation of inferences and results from the MACS data.